Introduction: CrossFit Style Plyo Box (ShopBot!)

This is my second attempt at a plyo box. This time in technicolor! I took a ShopBot class at TechShop and decided it would work better than the inaccuracies of the table saw and band saw.

Materials:

3/4" sheet of plywood (I chose a birch variety)

Two-flute end mill (I chose 1/4")

Sandpaper

Screws (at least 1.5 in long)

Tools:

Shopbot

End Mill

Drill bit (1/8")

Brass screws (long enough to go through material; 1.5")

Step 1: Creation of the Plans

I detailed in my other instructable that I modified a few plans to get to one I liked. I mocked up the same plans in Illustrator which is the one of the pictures in this step. I was able to include the drill holes here as well. I planned on using the edges to my advantage to minimize cuts, this wasn't the best choice and I will tell you why later in the next step.

Here is the file that I put together with Adobe Illustrator. It is in a public file from dropbox.

File

Step 2: Importing Into VCarv

TechShop uses VCarv for their CAD to CAM uses. Simple open an illustrator file into VCarv to get started.

This is where I had a few issues. Two of my drill holes were now simply lines. I used the create circle feature to recreate my holes. It was easy to dictate their size and position.

The other issue I ran into was all my pieces were not closed vectors. I had been planning to use all my edges on the edge of the board but was advised against it. It was a good choice to bump all my pieces in since there was no easy way to center my plywood on the ShopBot later. In VCarv there is a tool to close open vectors with a straight line and I used it to close my vectors.

I also set my material thickness and chose my tools in VCarv at this point. With the realization that my material thickness would change once I had a caliper to measure it.

Tabs - I was advised on using minimal tabs. I settled on two per piece and none for my handles.

Speeds - I paid less attention to the speed of my cut than I probably should have, but I settles on 3"/sec I believe. Proper research into the type of material and appropriate speeds would be ideal.

Remember to change your material thickness once you have it and can measure it with a caliper.

Here is the Vcarv file I used. I made a few changes on the fly once I was at the shopbot so I won't guarantee it's perfect but it will get you 90% there.

VCarv File

Step 3: Setting Up the ShopBot and Drilling Holes

For this step, the basics will be covered in your ShopBot class at TechShop but I will cover them in high level here.

I like to zero the X and Y coordinates out for the whole table first, then zero out the Z coordinates to the plate. You do this by visiting the Cut menu for both commands.

I learned here that there isn't really a good way to check and make sure your material is square. If you wanted you could line up the bit with a corner on one end, run the router to the other end and check that way. I trusted the sacrificial boards that TechShop had placed were good enough and they were.

I measured where the anchors for my material should go so they were out of the way and drilled holes for the brass wood screws. Brass will apparently not shatter your bit at high speeds so is one of the few safe materials to use to secure your material.

I drilled all the holes in my piece first. I used an 1/8th" drill bit and the whole thing took about 1.5 minutes to drill the roughly 20 holes.

Step 4: Cutting the Handles

I decided to use these angled handles I saw online. I feel like they give a better angle for your hands when you reach around to carry the box.

I changed out the drill bit for my 1/4" end mill. I re-zeroed the machine in all three coordinates (Cuts menu once again) and then set to work. I checked the depth of my work at the end and it hadn't really gotten into the sacrificial board so my caliper measurements were spot on.

Note: I didn't use any tabs on this portion of the cuts, and in hind sight might have been smart. The pieces essentially broke loose towards the end and it could have been problematic if they had caught the end mill and flew out.

Note: I used an air hose to keep the work area as clean as possible. The air compressor pump was turned off halfway through this cut and I had to turn it on again after.

Step 5: Cutting the Main Pieces

Short story here: Re-zero all three coordinates and run your program.

Note: I paused my cuts partway through my job and it caused some issues with my job (it cut into the sacrificial board some). I would avoid pausing a job at all costs and if you do, take the time to figure out what line of G Code you are at, stop your process, re-zero your coordinates and run your piece from that line of G code. These machines are not really set it and forget it. You do have to watch it and know what's going on with your piece.

Step 6: Some Finishing Touches - Sanding and Counter Sink

When jumping on a box for box jumps the last thing you want are sharp corners for your shins to get ripped up on. The other thing you will notice is the "stings" attached to the board. I cleaned up the edges of all my boards with a belt sander set at 90 degrees.

I also 'rounded' the edges of all my outside corners to prevent the above-mentioned shin damage. To do this I set the disc sander to 45 degrees and applied the edges to the disc sander.

Safety Note: When putting wood onto a disc sander make contact with the disc on the downward side. If you come into contact with the other side first your material can flip up out of your hands and hurt you.

The penultimate step is to counter sink all your drilled holes and pre-drill into your edges with the box together. The last thing you want is to crack your wood after all this work so pre-drilling helps prevent that.

Step 7: Assembly and Finish

When I got to this step I realized two things. The joints were tight. I had to use a rubber mallet to get the box together. I probably could have jumped on it a few times without screws, but I advise against it. If I were to do it again, I have been advised to give a .05" clearance on either side of the joint in my CNC plans. That being said, a little sanding does the trick too.

Grab some screws and throw the box together. I started from the top and worked my way down. Eventually putting the box on the side to secure the bottom.

You can stain, or paint the box any color your want. I will probably laser etch something on the ends. For now I'm leaving it untreated. I will steer away from anything oil based that doesn't dry hard that you could slip on.

I have seen some people put a fine sand in a wet coat of stain, let it dry and stain/poly varnish over it to give the box some grip to the top...I'm just ready to start jumping.

...and remember, I made it at TechShop!

Comments

author
CoastalDrifter made it! (author)2015-01-18

If you use a 3/4 in veneer and a few 1x2's or 2x2's it should be more than enough. Just frame the inside and a brace in the middle of each piece. You can actual use this for three different heights if you reinforce it right.

author
chrisgrames made it! (author)chrisgrames2015-01-18

I really feel it is strong enough without any bracing inside already. Certainly it's strong enough in the narrow directions, and the widest (24" tall) which is what use the most, I feel comfortable without any bracing. Of course, better safe than sorry.

author
denisemoore made it! (author)2014-06-03

Thanks for the directions, is the plyo box strong enough on it's own for someone 220lbs? Or should it be reinforced with 2x4s?

author
chrisgrames made it! (author)chrisgrames2014-06-05

I wouldn't be able to give you an answer confidently since I am not 220lbs or an engineer. While the box feels sturdy to me, the boxes that get sold by gyms and equipment manufacturers almost always have a center piece internally for reinforcement.

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